Steam turbine



March 17, 1925. G. FORNER STEAM TURBINE Filed April 19, 1924 tion.

Patented Mar. 17, 1925;

GEoRe'Fo'RNE-R, oF-j'nnnn n; enniv mity hssienogn no ieMENGES BnsOHA-FTBROWN,

BovERI AND(CI'E.','10F 'QBZADEN, SWITZERLAND.

enema-E.

zen of the German "*RepabIi-e, fesiding at Berlin, (lre'i'unaiiy, haveinvented-certain new and useful Improvements "in SteamTiirthestaged1"op,*thealte tion 5 does 'not occur bines.

of "which tli'e following "is P a specifica- This invention fiel-a'tes{to steam turbine velocity stages 'ti'ltll sliglit reaemon and moreparticularly =to-"a -mosey-stag where in a sllgh-t expansion takes'plaee'avith-in the v bladin'g. v

Suchstages have "already been eonstruted and also "described in-"theliterature "of "the art. In theset 'knoivn "stages the reaetio'n is verysmall and ocenrson lyfin thefirst rings of blades, and is not--l:'oiu.1d=i n the "othler rings of blades. That iman ne'r f Workinghas very zgiave diiawbaeks. :=Inwtpressu1-'e stages having no reaction'the relative velocit-y is'considerably (greater in the first ring thanin the last :ring of blades. Gonsequently' the 'i'otor -:-blad'es of thering'of blades are much longer than those 0f the first ring of "blades.This heivev'er, does not help theid'esigner; the lelfgth'O'CE the bladesin the first ring presents no d'ilii'cnl'ty to him, and "it llS I thelength of' th'e' blades -in the last row or rows of blades which hewould be glad to red-nee. I Those d'i 'a-wbaeks "of the known'eons'tru'otion are obvi'ated -'aecord-ing to the present invention byarranging for 'the expansion to take place only in these rings of bladesin which the relative entrance velocity is less than the velooityofsound.

This Will be correct in niostea'sesonly Tor the last rings of blades. Ofpartictlla'r iadvantage-in thisi'i'nproved'conneotion is the arrangementthat the expansion in the blades iso'arried "onlyfto-sue h an extentthat the relative =-eXit velocity is less {than the velocity ofso'und.Byth-is means the drawback is avoided that when .the yeloeity' of soundis greatly exceeded, the blade piassages would have to "beeoii'stru'eted "the form of sum-gee nozzles if a 'eons'i'derahledeflection '0" ies-tea'ln'fjet i's'not' desired. many cases it is notaflvant g eens to allow the expansion to exceed, inthe nozzles, thevelocity 'ofsoun'd.

This invention allows the last blades to be made much shorter than inthe case of no or only a slight reaction according to the known process,with theresult that rotor frition is "diminished, and owin to theis'lhzrller tli vergehcefo fth'e steam jets a "higher eliifcleney isattained. AFt'urther 'a'dvantage {is that the 1"otor"cl1inens1ons "can-b'e "so proo'itioiiedthat When ai teration'o'ce'uiis in 'iinone 'i'ingof blades eloneer in the nozzles alone, we thus avoids large "impactlosses.

It is also advisable to"distributethe'atldipansioiwdrep 'overfi the;rings of bla-desthat eom n qa'estien in'isuehianianiler-that th'eirelavefinicrease in the kinetie energy in :th-e inings 0f bla d'es i's' in ix' erse proportion to the rela'ltiveentrance velocity. It is advisableto arrange the f'expansion in the rings "of blades in -'sueh a 'mannerthat the aeomponent of the relativefiexi t 'Velooity atri g ht -anglesto tlle'direetio n of thei'zperipheral a eloei-ty isapproximatelyei1ua-l in the Tings of'blads? that come in :q-uestion. Theaccompanying drawings illustrate one Way ofoaf'itying the invention into"efieet.

1"is"=adiag nan1 of the pressures in "the different sta'ge'sefltnow'n'tui' bine's.

Figs 2 is a velooity diagram eorrespo-nd to "the same.

Fig. 3- rep'r'esents diagrammatiea ll the improved turbine in section,throu h one nozzle, two pairs of retort-blades "and-one pair ofstationary gn'ide blades of the half turbine sho-wn in sectional"elevation in ig.5 is a diagram oftlie' pres sures in thediflerentstages of e-i i n-proved turbine. V

6f'i's a verse y-diagram eriespmiding to'th'e same; h 1

and A 'iiidi 1 e 'the nozzles for'thfe' old and the new arrangementrespeetive'ly, B, D and "In s. 1"a nd Sft-he lines ti arers'in h, B, ,3A, G; rep'i esent by their iglit the mapamrive -p ressiires intheeesp-eetive-stages. i

essu e in the 1105216. A is eom leteivvelocity from B is also greaterthan the critical velocity so that the channel between the individualblades of B must also be cons 'structed so as to diverge on the outletside by suitably profiling the blades. Similarly, the steam passes intothe guide blades C and from there to the second rim D of the rotorwheel. Since, in this case, the whole'blading works at the samepressure, no energy is supplied, apart from that due team outletVelocity from the nozzle, so that the velocity decreases not only owingto the outputbut also owing to the friction in the blades. The result ofthis is that for the purpose of enlarging the channels for the flowbetween the blades the outletangle from the blades must grow continuallylarger and the radial I. D increase at the samet1me.

len th of theblades must also substantially In the present invention,the steam energy in the nozzle is not converted into speed wlth the fullavailable pressure drop since, as shown in Figures3 and 4,the nozzle andthe blading of the wheel is so dimensioned that in the, nozzleA"a'pproximately critical velocity isattained, so that the relativeentrance-velocity into the first rotor blades lies just below thecritical velocity. Naturally, then, the relative exit velocity from thisfirst row of moving blades B also lies below the critical velocity. Thevelocity through the reversing row of blades G" decreases again,butaccording to the presentinvention apart of the still available pressuredrop is to be used in order to bring the veishing of the exit surfaceofthe reversing guide blade-C and of the second blade rim D is'made inconjunction with the decrease in the exit velocity from the nozzles Aand v the subsequent increase in the velocities in the reversing guideblade C and the second 'row of moving blades D. The radial dimensions ofthe nozzles A and possibly of the first ring of blades B is thereforegreater in the proposed blading than in the usual- I constant pressureblading and, on the other hand, the blading of the reversing guide bladeC and of the second rimD is smaller.

In the usual constant pressure turbine stage, knownas a velocity stage,the whole pressure energy of the working steam is cqn Y dividual blades.

locity O-R.

Similarly for the reverse segment or guide blade ring I get the absoluteentrance velocity O-S and absolute exit velocity O-T, and lastly for thesecond rotor rim the relative velocity at the entrance O U' and therelative velocity at the outlet'O.V or the absolute outlet velocity OW."

In view of the fact that during the whole operation no more energy issupplied, the

said velocities continually decrease.

In the blading according to the invention, in addition to theconversionof the major portion of the available pressure energy of thesteam into the velocity O"P-, a, moderate conversion also takes place inthe in- The velocities O+R, O,S, OT, O'-U", OV and OVV thereforedecrease much less andin consequence the blading smaller radialdimensions.

What I claim is 1. A steam turbine velocity stage with slight reaction,in which the reaction eiiect takes place only in the last blades inwhich the relative entrance velocity is smaller than the so-calledcritical velocity.

2. A steam turbine velocity stage as. claimed in claim 1, wherein theexpansion in the blades is carried only to such adegr'ee that therelative exit velocity is smaller than the velocity of sound.

3. A steam turbine. velocity stage as claimed in claim 1, wherein thenozzles are in the form of non-enlarged guide devices, the expansion inthese nozzles being carried alteration has efiiect inmore than one ringof blades. v 6. A steam turbine velocity stage as claimed'in claim 1,wherein the axial component of the exit velocity is approximately thesame in all the rings of blades.

" In testimony whereof I have signed my name to this specification. ,2 IGEORG FORNER.

may be made of n only to such a degree that the velocity of

